Esters Of Structurally Symmetric Alkoxylated Polyols And Applications Thereof

ABSTRACT

In one aspect, compositions are described herein. In some embodiments, a composition comprises an ester reaction product of a structurally symmetric alkoxylated polyol and a carboxylic acid or carboxylic acid equivalent. In some embodiments, the structurally symmetric alkoxylated polyol comprises an alkoxylated pentaerythritol, dipentaerythritol, tripentaerythritol, higher oligomer of a pentaerythritol, or a combination thereof.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority pursuant to 35 U.S.C. §119(e) to U.S. Provisional Patent Application Ser. No. 61/485,932, filed on May 13, 2011, which is hereby incorporated by reference in its entirety.

FIELD

This invention relates to esters and applications thereof, and, in particular, to esters of structurally symmetric alkoxylated polyols.

BACKGROUND

Lubricants are used in a wide range of industrial and consumer products and applications, including engines and cosmetics as well as metal working, drilling, and manufacturing processes. Different applications often require different lubricant characteristics. Further, lubrication performance can be affected simultaneously by a number of factors such as the lubricant's molecular weight, viscosity, viscosity index, and melting point or pour point. Moreover, many lubricants simultaneously exhibit both desirable and undesirable properties for a given application.

Accordingly, a need exists for lubricants that exhibit a combination of properties useful for various lubrication applications.

SUMMARY

In one aspect, compositions are described herein. In some embodiments, a composition comprises an ester reaction product of a structurally symmetric alkoxylated polyol and a carboxylic acid. In some embodiments, a composition comprises an ester reaction product of a structurally symmetric alkoxylated polyol and a carboxylic acid equivalent such as an anhydride, acid chloride, or methyl ester of a carboxylic acid. A structurally symmetric alkoxylated polyol, in some embodiments, comprises an alkoxylated pentaerythritol, dipentaerythritol, tripentaerythritol, higher oligomer of a pentaerythritol, or a combination thereof. Moreover, in some embodiments, a structurally symmetric alkoxylated polyol is prepared from an alkene oxide and a structurally symmetric polyol. In addition, in some embodiments of compositions described herein, the center of mass of a structurally symmetric alkoxylated polyol is about 1000 picometers (pm) or less from the central atom of the structurally symmetric alkoxylated polyol. Moreover, compositions described herein, in some embodiments, can be used as lubricants.

In another aspect, lubricants are described herein. In some embodiments, a lubricant comprises a composition comprising one or more ester reaction products of a structurally symmetric alkoxylated polyol and a carboxylic acid or carboxylic acid equivalent. Moreover, in some embodiments, a lubricant has a viscosity index of about 150 or more and/or a pour point below about −10° C. In some embodiments, a lubricant has a molecular weight and viscosity at 25° C. within a graphical region defined by a ±10% vertical offset of the line defined by the equation y=0.0649x+11197, where y is the viscosity at 25° C. in cS and x is the molecular weight, the molecular weight being greater than about 800. In other embodiments, a lubricant has a molecular weight and viscosity at 25° C. within a graphical region defined by a ±10% vertical offset of the line defined by the equation y=0.1008x−74.655, where y is the viscosity at 25° C. in cS and x is the molecular weight, the molecular weight being greater than about 800. Further, in some embodiments, a lubricant described herein does not comprise a silicone or does not comprise a substantial amount of a silicone.

In another aspect, methods of making an ester are described herein. In some embodiments, a method of making an ester comprises alkoxylating a structurally symmetric polyol with an alkene oxide to provide a structurally symmetric alkoxylated polyol and esterifying the structurally symmetric alkoxylated polyol with a carboxylic acid, wherein at least 70% of the hydroxyl groups in the structurally symmetric alkoxylated polyol are esterified. Alternatively, in some embodiments, esterifying is carried out using a carboxylic acid equivalent. In some embodiments, a structurally symmetric polyol comprises a pentaerythritol, a dipentaerythritol, a tripentaerythritol, a higher oligomer of a pentaerythritol, or a combination thereof. Further, in some embodiments, an alkene oxide comprises ethylene oxide, propylene oxide, butylene oxide, or a combination thereof. A carboxylic acid, in some embodiments, comprises a saturated carboxylic acid having 2 to 26 carbon atoms. A carboxylic acid equivalent, in some embodiments, comprises an anhydride, acid chloride, or methyl ester of a carboxylic acid.

These and other embodiments are described in greater detail in the detailed description which follows.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a graph illustrating the relationship between the viscosity and molecular weight of a series of known lubricant materials and two series of lubricants according to some embodiments described herein.

FIG. 2 is a graph illustrating the relationship between the viscosity and molecular weight of a series of known lubricant materials and a domain of lubricants according to some embodiments described herein

DETAILED DESCRIPTION

Embodiments described herein can be understood more readily by reference to the following detailed description, examples, and drawing. Elements, apparatus and methods described herein, however, are not limited to the specific embodiments presented in the detailed description, examples, and drawing. It should be recognized that these embodiments are merely illustrative of the principles of the present invention. Numerous modifications and adaptations will be readily apparent to those of skill in the art without departing from the spirit and scope of the invention.

In addition, all ranges disclosed herein are to be understood to encompass any and all subranges subsumed therein. For example, a stated range of “1.0 to 10.0” should be considered to include any and all subranges beginning with a minimum value of 1.0 or more and ending with a maximum value of 10.0 or less, e.g., 1.0 to 5.3, or 4.7 to 10.0, or 3.6 to 7.9.

I. Compositions

In one aspect, compositions are described herein. In some embodiments, a composition comprises an ester reaction product of a structurally symmetric alkoxylated polyol and a carboxylic acid. In some embodiments, a composition comprises an ester reaction product of a structurally symmetric alkoxylated polyol and a carboxylic acid equivalent, such as an anhydride, acid chloride, or methyl ester of a carboxylic acid. Moreover, in some embodiments, the structurally symmetric alkoxylated polyol retains its structural symmetry.

A “structurally symmetric” alkoxylated polyol, in some embodiments, has a structure exhibiting at least one symmetry element associated with a symmetry operation from group theory other than the identity element. A non-identity symmetry element, for example, can comprise an n-fold rotation axis, a mirror plane, or another symmetry element from group theory. Further, the non-identity symmetry element is based on an equilibrium or average molecular shape at standard temperature and pressure, as opposed to a transient or short-lived molecular conformation. Moreover, in some embodiments, a “structurally symmetric” alkoxylated polyol comprises an alkoxylated polyol having a central tetrahedral atom. In some embodiments, a “structurally symmetric” alkoxylated polyol comprises an alkoxylated polyol having a dendritic structure. The term “structurally symmetric” is contemplated to include any or all of the foregoing meanings. Moreover, in some embodiments, the structurally symmetric alkoxylated polyol comprises more than two hydroxyl groups.

Any structurally symmetric alkoxylated polyol not inconsistent with the objectives of the present invention may be used. For instance, in some embodiments, a structurally symmetric alkoxylated polyol comprises a structurally symmetric ethoxylated polyol. In some embodiments, a structurally symmetric alkoxylated polyol comprises an alkoxylated pentaerythritol. In other embodiments, a structurally symmetric alkoxylated polyol comprises an alkoxylated dipentaerythritol or an alkoxylated tripentaerythritol. In some embodiments, a structurally symmetric alkoxylated polyol comprises an alkoxylated higher oligomer of a pentaerythritol or a combination of an alkoxylated pentaerythriol, dipentaerythritol, tripentaerythritol, or higher oligomer of a pentaerythritol (n>3).

In addition, in some embodiments of compositions described herein, a structurally symmetric alkoxylated polyol is prepared from an alkene oxide and a structurally symmetric polyol. A “structurally symmetric” polyol, in some embodiments, comprises a polyol having a structure exhibiting at least one symmetry element associated with a symmetry operation other than the identity operation. In some embodiments, a “structurally symmetric” polyol comprises a central tetrahedral atom. In some embodiments, a “structurally symmetric” polyol comprises a polyol having a dendritic structure. The term “structurally symmetric” is contemplated to include any or all of the foregoing meanings. Moreover, in some embodiments, a structurally symmetric polyol has more than two hydroxyl groups. Any structurally symmetric polyol not inconsistent with the objectives of the present invention may be used. In some embodiments, a structurally symmetric polyol comprises pentaerythritol, dipentaerythritol, and/or tripentaerythritol. In some embodiments, a structurally symmetric polyol comprises a higher oligomer of pentaerythritol. Moreover, in some embodiments, a structurally symmetric polyol comprises a mixture or combination of one or more of a pentaerythritol, a dipentaerythritol, a tripentaerythritol, and a higher oligomer of a pentaerythritol.

Similarly, any alkene oxide not inconsistent with the objectives of the present invention may be used. In some embodiments, for example, an alkene oxide comprises one or more of ethylene oxide, propylene oxide and butylene oxide. Further, in some embodiments, a structurally symmetric alkoxylated polyol described herein may be prepared by reacting 1 to 200 moles of alkene oxide with 1 mole of structurally symmetric polyol. In some embodiments, a structurally symmetric alkoxylated polyol may be prepared by reacting 1 to 50 moles of alkene oxide with 1 mole of structurally symmetric polyol.

In addition, in some embodiments, the center of mass of a structurally symmetric alkoxylated polyol of a composition described herein is close to the central atom of the structurally symmetric alkoxylated polyol. A central atom, in some embodiments, comprises an atom at which a symmetry element of the molecule is located or through which a symmetry element passes. In some embodiments, the center of mass of a structurally symmetric alkoxylated polyol is about 1000 pm or less from the central atom of the structurally symmetric alkoxylated polyol, where the distance is based on an equilibrium or average geometry of the molecule at standard temperature and pressure. In some embodiments, the center of mass is about 500 pm or less or about 200 pm or less from the central atom.

Esters of compositions described herein, in some embodiments, are prepared from a structurally symmetric alkoxylated polyol and a carboxylic acid or are reaction products of a structurally symmetric alkoxylated polyol and a carboxylic acid. Any carboxylic acid not inconsistent with the objectives of the present invention may be used. For example, in some embodiments, a carboxylic acid comprises a saturated carboxylic acid. Alternatively, in other embodiments, a carboxylic acid comprises an unsaturated carboxylic acid. Further, a carboxylic acid can be branched or linear. In addition, a carboxylic acid can be aliphatic or aromatic. In some embodiments, a carboxylic acid comprises a synthetic carboxylic acid. In other embodiments, a carboxylic acid comprises a naturally-occurring carboxylic acid. In some embodiments, a carboxylic acid comprises more than one carboxylic acid moiety. For instance, in some embodiments, a carboxylic acid comprises a dicarboxylic acid or a higher polyacid. In some embodiments comprising a dicarboxlyic acid or higher polyacid, the dicarboxylic acid or higher polyacid comprises no more than about 20 weight percent of the total amount of carboxylic acid used. In some embodiments, less than about 10 weight percent or less than about 5 weight percent dicarboxylic acid or higher polyacid is used. In some embodiments, a carboxylic acid has 6 to 26 carbon atoms. Moreover, in some embodiments, a carboxylic acid comprises a mixture or combination of one or more of the foregoing types of carboxylic acids. In some embodiments, a carboxylic acid comprises oleic acid, linoleic acid, linolenic acid, erucic acid, or a combination thereof. In other embodiments, a carboxylic acid comprises isostearic acid, monomer acid, or a combination thereof. In some embodiments, a carboxylic acid comprises pentanoic acid, heptanoic acid, 2-ethylhexanoic acid, pelargonic acid, a Guerbet acid, an α-methyl acid, an α,α-dimethyl acid, or a combination thereof. In some embodiments, a carboxylic acid comprises benzoic acid, methyl benzoic acid, or a combination thereof. In some embodiments, a carboxylic acid comprises oxalic acid, succinic acid, maleic acid, adipic acid, azelaic acid, sebacic acid, dodecanedioic acid, phthalic acid, isophthalic acid, terephthalic acid, or an anhydride thereof. In some embodiments, a carboxylic acid comprises trimellitic anhydride polyacid.

In addition, esters of compositions described herein, in some embodiments, are prepared from a structurally symmetric alkoxylated polyol and a carboxylic acid equivalent, or are reaction products of a structurally symmetric alkoxylated polyol and a carboxylic acid equivalent. A carboxylic acid equivalent, in some embodiments, comprises a methyl ester of a carboxylic acid described herein. In some embodiments, a carboxylic acid equivalent comprises an anhydride or acid chloride of a carboxylic acid described herein. Any methyl ester, anhydride, or acid chloride not inconsistent with the objectives of the present invention may be used.

Moreover, an ester reaction product of a composition described herein can have any structure not inconsistent with the objectives of the present invention. In some embodiments, a composition comprises at least one ester having the structure of Formula (I):

wherein

-   R₁ is —CH₂CH₂—,

where x is 1-10;

-   R₂, R₃, R₄, and R₅ are independently —H or —C(O)R₁₀, where R₁₀ is an     alkyl, alkenyl, or aryl group having 2 to 26 carbon atoms, provided     at least 3 of R₂, R₃, R₄ and R₅ are —C(O)R₁₀; and -   y is 1-50 or 1-20 or 1-10.

In some embodiments, all four of R₂, R₃, R₄ and R₅ are —C(O)R₁₀. In some embodiments, at least about 70% of the hydroxyl groups of the symmetric alkoxylated polyol are esterified. In some embodiments, at least about 80%, at least about 85%, at least about 90% or at least about 99% of the hydroxyl groups are esterified. In some embodiments, between about 95% and about 100% of the hydroxyl groups of the symmetric alkoxylated polyol are esterified.

In other embodiments, a composition comprises at least one ester having the structure of Formula (II):

wherein

-   R₁ is —CH₂CH₂—,

where x is 1-10;

-   R₂, R₃, R₄, R₅, R₆, and R₇ are independently —H or —C(O)R₁₀, where     R₁₀ is an alkyl, alkenyl, or aryl group having 2 to 26 carbon atoms,     provided at least 4 of R₂, R₃, R₄, R₅, R₆, and R₇ are —C(O)R₁₀; and -   y is 1-50 or 1-20 or 1-10.

In some embodiments, at least 5 of R₂, R₃, R₄, R₅, R₆, and R₇ are —C(O)R₁₀. In some embodiments, at least 6 of R₂, R₃, R₄, R₅, R₆, and R₇ are —C(O)R₁₀. In some embodiments, at least about 70% of the hydroxyl groups of the symmetric alkoxylated polyol are esterified. In some embodiments, at least about 80%, at least about 85%, at least about 90% or at least about 99% of the hydroxyl groups are esterified. In some embodiments, between about 95% and about 100% of the hydroxyl groups of the symmetric alkoxylated polyol are esterified.

In some embodiments, a composition comprises at least one ester having the structure of Formula (III):

wherein

-   R₁ is —CH₂CH₂—,

where x is 1-10;

-   R₂, R₃, R₄, R₅, R₆, R₇, R₈, and R₉ are independently —H or —C(O)R₁₀,     where R₁₀ is an alkyl, alkenyl, or aryl group having 2 to 26 carbon     atoms, provided at least about 70% of R₂, R₃, R₄, R₅, R₆, R₇, R₈,     and R₉ are —C(O)R₁₀; -   y is 1-50 or 1-20 or 1-10; and -   z is 1-10.

In some embodiments, at least about 80% of R₂, R₃, R₄, R₅, R₆, R₇, R₈, and R₉ are —C(O)R₁₀. In some embodiments, at least about 85%, at least about 90% or at least about 99% of the hydroxyl groups of the symmetric alkoxylated polyol are esterified. In some embodiments, between about 95% and about 100% of the hydroxyl groups are esterified.

Compositions described herein can be used in various applications. For example, in some embodiments, a composition described herein can be used as a lubricant, including a liquid lubricant. Lubricants comprising compositions described herein are further described hereinbelow in Section II.

II. Lubricants

In another aspect, lubricants are described herein. A lubricant, in some embodiments, comprises a composition described hereinabove in Section I. Any composition of Section I not inconsistent with the objectives of the present invention may be used. For example, in some embodiments, a lubricant comprises a composition comprising at least one ester having the structure of Formula (I), Formula (II), or Formula (III). In some embodiments, a lubricant comprises a composition comprising an ester reaction product of a structurally symmetric alkoxylated polyol and a carboxylic acid or carboxylic acid equivalent, including wherein the center of mass of the structurally symmetric alkoxylated polyol is about 1000 pm or less from the central atom of the structurally symmetric alkoxylated polyol.

Moreover, lubricants described herein, in some embodiments, exhibit one or more desirable properties. For a liquid lubricant, relevant properties can include (a) molecular weight or molar mass, (b) viscosity, (c) viscosity index, and/or (d) melting point or pour point. In general, the molecular weight or molar mass of a lubricant relates directly to inherent film strength of the lubricant fluid film. When a lubricant is under pressure between two surfaces, the ease with which the fluid film is pushed out of a pressure gap is inversely related to the lubricant's molecular weight. Higher molecular weight lubricants move more slowly and as a result, they have higher inherent film strength. As used herein, the terms “molecular weight” and “molar mass” refer to a substance's mass per mole. Further, where appropriate, the terms “molecular weight” and “molar mass” refer to the weight average molar mass, as opposed to the number average molar mass.

The viscosity of a lubricant relates directly to a lubricant's ability to reduce the friction between two surfaces under hydrodynamic lubrication conditions. Hydrodynamic lubrication results when, at high speed, there exists a fluid film between the two surfaces that are being lubricated. The friction between the two surfaces is directly related to the viscosity of the fluid in the lubricant film. Viscosity of a lubricant can be measured according to ASTM D445, the entirety of which is hereby incorporated by reference.

The viscosity index of a lubricant is a measure of the rate at which the viscosity of the lubricant changes with temperature. Viscosity index is typically measured on a “0 to 300” scale, with low numbers indicating that the viscosity changes rapidly with changes in temperature and high numbers indicating that the viscosity changes slowly with changes in temperature. Viscosity index, in some embodiments described herein, can be determined according to ASTM D2270, the entirety of which is hereby incorporated by reference. In some embodiments, viscosity index is calculated using equation (1):

VI=100×(L−U)/(L−H)   (1),

where VI is viscosity index, U is the kinematic viscosity at 40° C., and L and H are values based on the kinematic viscosity at 100° C., as described in ASTM D2270.

The melting point or pour point of a lubricant is a measure of the lubricant's ability to function under low temperature conditions without solidifying. The pour point is the minimum temperature at which a liquid lubricant will flow. The pour point can be measured according to ASTM D97, the entirety of which is hereby incorporated by reference.

A lubricant described herein, in some embodiments, can exhibit an unexpectedly high viscosity index. In some embodiments, a lubricant described herein has a viscosity index above 110, such as when measured according to ASTM D2270. In some embodiments, a lubricant has a viscosity index above 140. In some embodiments, a lubricant described herein has a viscosity index of about 150 or more. In some embodiments, a lubricant has a viscosity index of about 200 or more or about 250 or more. In some embodiments, a lubricant has a viscosity index between about 150 and about 250 or between about 200 and about 250.

Further, a lubricant described herein, in some embodiments, can also exhibit an unexpectedly low melting point or pour point. In some embodiments, a lubricant has a pour point below about −10° C., such as when measured according to ASTM D97. In some embodiments, a lubricant has a pour point below about −30° C. or below about −40° C. In some embodiments, a lubricant described herein has a pour point between about −10° C. and about −55° C., between about −30° C. and about −55° C., or between about −40° C. and about −55° C.

A lubricant described herein, in some embodiments, can also exhibit both a high viscosity index and a low pour point. In some embodiments, for example, a lubricant has a viscosity index between about 150 and about 250 and a pour point between about −10° C. and about −55° C.

A lubricant described herein, in some embodiments, can also exhibit an unexpected relationship between molecular weight and viscosity. For instance, in some embodiments, a lubricant described herein has an unexpectedly low viscosity for a given molecular weight or an unexpectedly high molecular weight for a given viscosity.

FIG. 1 is a graph illustrating the relationship between the viscosity and molecular weight of a series of known lubricants (Series A) and two series of lubricants according to some embodiments described herein (Series B and C). Series A is a composite of numerous known lubricant materials, such as mineral oils, short chain (C8-C10) ester and polyol ester lubricants, polyethylene glycol (PEG) diesters, and poly alpha olefins. The molecular weight and viscosities of many known lubricant materials fall on or very close to the viscosity-molecular weight relationship of Series A. The viscosity-molecular weight relationship of Series A can be described by equation (2):

y=0.185x−74.0   (2),

wherein y is the viscosity at 25° C. in centistokes (cS), x is the molecular weight, and R²=0.9987.

In contrast, lubricants described herein, in some embodiments, exhibit viscosity-molecular weight relationships that fall below the line of Series A and thus exhibit lower than expected viscosities for a given molecular weight as illustrated, for example, by the lines of Series B and Series C. Further, in some embodiments, such lubricants are silicone-free or substantially silicone-free. The viscosity-molecular weight relationship of Series B in FIG. 1 can be described by equation (3):

y=0.0649x+12.197   (3),

wherein y is the viscosity at 25° C. in cS, x is the molecular weight, and R²=0.979.

The viscosity-molecular weight relationship of Series C in FIG. 1 can be described by equation (4):

y=0.1008x−74.655   (4),

wherein y is the viscosity at 25° C. in cS, x is the molecular weight, and R²=0.9813.

Tables 1 and 2 below provide data points of Series B and C, respectively, where the lubricants in the Tables were prepared from the listed polyols, alkene oxides, and carboxylic acids as described herein.

TABLE 1 Series B Viscosity Molecular Alkene Carboxylic at 25° C. Weight Series B Polyol Oxide Acid (cS) (g/mol) Lubricant penta- ethylene pelargonic 67 916 1 erythritol oxide acid Lubricant penta- propylene pelargonic 91 1160 2 erythritol oxide acid Lubricant penta- ethylene pelargonic 99 1356 3 erythritol oxide acid

TABLE 2 Series C Viscosity Molecular Alkene Carboxylic at 25° C. Weight Series C Polyol Oxide Acid (cS) (g/mol) Lubricant dipenta- ethylene pelargonic 95 1638 4 erythritol oxide acid Lubricant dipenta- ethylene caprylic 85 1650 5 erythritol oxide acid/capric acid (60/40%) Lubricant dipenta- ethylene coconut oil 125 1950 6 erythritol oxide fatty acid (COFA) Lubricant dipenta- ethylene oleic acid 167 2410 7 erythritol oxide

In some embodiments, a lubricant described herein has a molecular weight and viscosity at 25° C. within a graphical region defined by a ±10% vertical offset of the line defined by equation (3) above, wherein the molecular weight is greater than about 800. In some embodiments, the molecular weight is greater than about 900 or greater than about 1000. In some embodiments, the molecular weight is between about 900 and about 2500 or between about 900 and about 1500. In some embodiments, the molecular weight is between about 800 and about 6000. Further, in some embodiments, a lubricant has a molecular weight and viscosity at 25° C. within a graphical region defined by a ±15% vertical offset or within a graphical region defined by a ±5% vertical offset of the line defined by equation (3) above. For example, in some embodiments, a lubricant may have a molecular weight of 1000 and a viscosity at 25° C. of 82 cS. The ordered pair (1000, 82) has a vertical offset of about 6.5% from the line defined by equation (3), because the absolute value of (77−82) is about 6.5% of 77, where 77 is the value of y for x=1000 in equation (3). Therefore, the lubricant has a molecular weight and viscosity at 25° C. within a graphical region defined by a ±15% or a ±10% vertical offset of the line defined by equation (3) above.

In other embodiments, a lubricant described herein has a molecular weight and viscosity at 25° C. within a graphical region defined by a ±10% vertical offset of the line defined by equation (4) above, wherein the molecular weight is greater than about 800. In some embodiments, the molecular weight is greater than about 900, greater than about 1000, greater than about 1500, or greater than about 1700. In some embodiments, the molecular weight is between about 1000 and about 3000, between about 1500 and about 2500, or between about 2000 and about 5000. In some embodiments, the molecular weight is between about 800 and about 6000. Further, in some embodiments, a lubricant has a molecular weight and viscosity at 25° C. within a graphical region defined by a ±15% vertical offset or within a graphical region defined by a ±5% vertical offset of the line defined by equation (4) above.

Moreover, lubricants described herein, in some embodiments, exhibit viscosity-molecular weight relationships described by additional lines other than those of Series B and Series C. In some embodiments, lubricants described herein exhibit a viscosity at 25° C. and a molecular weight falling within the graphical region labeled Region 1 of FIG. 2, where Region 1 has an upper boundary defined by the line described by equation (5) and a lower boundary defined by the line described by equation (6):

y=0.12x   (5) and

y=0.023x+40   (6),

wherein y is the viscosity at 25° C. in cS and x is the molecular weight, the molecular weight being greater than about 800. In some embodiments, the molecular weight is greater than about 900, greater than about 1000, or greater than about 2000. In some embodiments, the molecular weight is between about 800 and about 1500, between about 1000 and about 2500, between about 1500 and about 3000, between about 2000 and about 5000, In some embodiments, the molecular weight is between about 800 and about 6000.

In some embodiments, a lubricant described herein has a viscosity at 25° C. between about 20 cS and about 100 cS and a molecular weight between about 750 and about 1500. In some embodiments, a lubricant has a viscosity at 25° C. between about 50 cS and about 100 cS and a molecular weight between about 850 and about 1400. In other embodiments, a lubricant has a viscosity at 25° C. between about 30 cS and about 200 cS and a molecular weight between about 1500 and about 2500. In some embodiments, a lubricant has a viscosity at 25° C. between about 75 cS and about 175 cS and a molecular weight between about 1500 and about 2500.

Moreover, lubricants described herein, in some embodiments, are silicone-free or substantially silicone-free. A silicone-free lubricant, in some embodiments, comprises no detectable amount of silicone. A substantially silicone-free lubricant, in some embodiments, comprises less than about 10 weight percent silicone or less than about 5 weight percent silicone. In some embodiments, a substantially silicone-free lubricant comprises less than about 1 weight percent or less than about 0.1 weight percent silicone. In some embodiments, a silicone-free or substantially silicone-free lubricant has a viscosity at 25° C. and a molecular weight within a graphical region defined by a 10% or greater vertical offset below the line defined by equation (2) above. In some embodiments, the viscosity at 25° C. and molecular weight are within a graphical region defined by a vertical offset of greater than 15% or greater than 20% below the line defined by equation (2) above. In some embodiments, a silicone-free or substantially silicone-free lubricant having a viscosity at 25° C. and molecular weight more than a 10% vertical offset below the line defined by equation (2) above has a molecular weight greater than about 800 or greater than about 1000. In some embodiments, the molecular weight is between about 800 and about 6000, between about 800 and about 3000, or between about 1000 and about 2500.

Lubricants described herein can have any combination of the foregoing properties not inconsistent with the objectives of the present invention. For example, in some embodiments, a lubricant has an unexpectedly low viscosity for a given molecular weight, a high viscosity index, and a low pour point. In some embodiments, a lubricant has at least two of, at least three of, at least four, or at least five of the following seven features, (i)-(vii):

-   -   (i) a viscosity index between about 150 and about 250 or between         about 200 and about 250;     -   (ii) a pour point between about −10° C. and about −55° C.,         between about −30° C. and about −55° C., or between about         −40° C. and about −55° C.;     -   (iii) a molecular weight and viscosity at 25° C. within a         graphical region defined by a ±10% vertical offset of the line         defined by equation (3) above;     -   (iv) a molecular weight and viscosity at 25° C. within a         graphical region defined by a ±10% vertical offset of the line         defined by equation (4) above;     -   (v) a molecular weight and viscosity at 25° C. within Region 1         above, the molecular weight being between about 800 and about         6000;     -   (vi) a viscosity at 25° C. between about 20 cS and about 100 cS         and a molecular weight between about 750 and about 1500; and     -   (vii) a viscosity at 25° C. between about 30 cS and about 200 cS         and a molecular weight between about 1500 and about 2500.         Further, in some embodiments, such a lubricant can be         silicone-free or substantially silicone-free. In addition, such         a lubricant can, in some embodiments, comprise a composition         described hereinabove in Section I.         III. Methods of making an Ester

In another aspect, methods of making an ester are described herein. In some embodiments, a method of making an ester comprises alkoxylating a structurally symmetric polyol with an alkene oxide to provide a structurally symmetric alkoxylated polyol and esterifying the structurally symmetric alkoxylated polyol with a carboxylic acid, wherein at least 70% of the hydroxyl groups in the structurally symmetric alkoxylated polyol are esterified. In some embodiments, at least 80% of the hydroxyl groups are esterified. In some embodiments, a method comprises esterifying a structurally symmetric alkoxylated polyol with a carboxylic acid equivalent instead of or in addition to a carboxylic acid. Further, in some embodiments, at least 85%, at least 90%, at least 95% or at least 99% of the hydroxyl groups are esterified.

Any structurally symmetric polyol not inconsistent with the objectives of the present invention may be used. In some embodiments, a structurally symmetric polyol comprises a structurally symmetric polyol described hereinabove in Section I. For example, in some embodiments, a structurally symmetric polyol comprises a pentaerythritol, a dipentaerythritol, a tripentaerythritol, a higher oligomer of a pentaerythritol, or a combination thereof. Moreover, any suitable structurally symmetric polyol can be used with any suitable alkene oxide and any suitable carboxylic acid or carboxylic acid equivalent to provide any desired ester not inconsistent with the objectives of the present invention.

Similarly, any alkene oxide not inconsistent with the objectives of the present invention may be used, including an alkene oxide described hereinabove in Section I. In some embodiments, for instance, an alkene oxide comprises ethylene oxide, propylene oxide, butylene oxide, or a combination thereof. Moreover, any suitable alkene oxide can be used with any suitable structurally symmetric polyol and any suitable carboxylic acid or carboxylic acid equivalent to provide any desired ester not inconsistent with the objectives of the present invention. For example, in some embodiments, the structurally symmetric polyol comprises a pentaerythritol, dipentaerythritol, or tripentaerythritol, and the alkene oxide comprises ethylene oxide.

In addition, any carboxylic acid not inconsistent with the objective of the present invention may be used. In some embodiments, a carboxylic acid comprises a carboxylic acid described hereinabove in Section I. For example, in some embodiments, a carboxylic acid comprises a linear chain saturated carboxylic acid having 2 to 26 carbon atoms. Moreover, any suitable carboxylic acid can be used with any suitable structurally symmetric polyol and any suitable alkene oxide to provide any desired ester not inconsistent with the objectives of the present invention. In some embodiments, choice of reactants can affect the properties of the resulting ester. For example, in some embodiments, choice of carboxylic acid or blend of carboxylic acids can permit tuning of the molecular weight and/or melting point of the resulting ester.

Moreover, any carboxylic acid equivalent not inconsistent with the objectives of the present invention may be used. In some embodiments, a carboxylic acid equivalent comprises a carboxylic acid equivalent described hereinabove in Section I. For example, in some embodiments, a carboxylic acid equivalent comprises one or more of a methyl ester, anhydride, or acid chloride of a carboxylic acid described herein.

Turning now to steps of methods, methods of making an ester described herein comprise alkoxylating a structurally symmetric polyol with an alkene oxide. Alkoxylation can be carried out in any manner not inconsistent with the objectives of the present invention. In some embodiments, for example, alkoxylating comprises reacting an alkene oxide with a structurally symmetric polyol. In some embodiments, alkoxylating comprises using an excess of alkene oxide. In some embodiments, alkoxylating comprises reacting 1 to 200 moles of alkene oxide per mole of symmetric polyol or 1 to 50 moles of alkene oxide per mole of symmetric polyol. Moreover, in some embodiments, alkoxylating comprises ethoxylating.

Methods of making an ester described herein also comprise esterifying a structurally symmetric alkoxylated polyol with a carboxylic acid or carboxylic acid equivalent. Esterification can be carried out in any manner not inconsistent with the objectives of the present invention. In some embodiments, for example, esterifying comprises heating a mixture of a structurally symmetric alkoxylated polyol and a carboxylic acid or carboxylic acid equivalent, including an aqueous mixture. In some embodiments, an esterification reaction comprises a condensation or dehydration reaction. Further, in some embodiments, esterifying is carried out in the presence of a catalyst. Any catalyst not inconsistent with the objectives of the present invention may be used. In some embodiments, for instance, a catalyst comprises a mineral acid catalyst. In some embodiments, a catalyst comprises hydrochloric acid and/or sulfuric acid. In some embodiments, a catalyst comprises p-toluene sulfonic acid and/or methane sulfonic acid. In some embodiments, a catalyst comprises a base catalyst. In some embodiments, a catalyst comprises sodium hydroxide and/or potassium hydroxide. In some embodiments, a catalyst comprises a neutral catalyst. In some embodiments, a catalyst comprises tin or titanium. In some embodiments, a catalyst comprises one or more of a tetraalkoxytitanate, stannous oxide, or an organic stannous or stannic salt.

Some embodiments described herein are further illustrated in the following non-limiting examples.

EXAMPLE 1 Composition comprising an Ester

A composition comprising an ester according to one embodiment described herein was prepared as follows. The composition was prepared using a standard high temperature laboratory esterification setup. A 1-liter, 4-neck round bottom flask reactor was set up and equipped with a heating mantle, mechanical agitation, nitrogen sparge, temperature controller and a short packed column connected to a condenser. To the flask were charged the following: 300 grams of pelargonic acid; 300 grams of POE (15) pentaerythritol (where “POE” stands for polyoxyethylene); and 0.60 grams of p-toluene sulfonic acid.

The reaction mixture was heated to 180° C. under slow nitrogen sparge. Then, over a period of three hours, the temperature was increased to 220° C. and held at this temperature for 2 hours. During that time, the acid value of the reaction mixture went to 30 mg of KOH per gram of material. The reaction mixture was cooled to 100° C., and the catalyst was neutralized with 0.30 grams of 50% sodium hydroxide. The packed column was removed, and a short path condenser/receiver was attached to the flask. Vacuum (˜0.5 mm) was applied to the flask, and the reaction mixture was heated to 230° C. and held at that temperature for 0.5 hours. During the distillation, the excess pelargonic acid was distilled over and recovered. The reaction mixture was cooled, the vacuum was released under nitrogen and the product was cooled to 80° C. and filtered through a bed of diatomaceous earth. The yield was 493 grams of the desired ester (96.4% of theory). The ester product had the following properties:

-   -   Acid value=0.4     -   Saponification value=166     -   Hydroxyl value=4.5     -   Viscosity @ 25° C.=99 cS (measured by CANNON FENSKE viscometer)     -   Viscosity @ 40° C.=58 cS (measured by CANNON FENSKE viscometer)

EXAMPLE 2 Composition comprising an Ester

A composition comprising an ester according to one embodiment described herein was prepared as follows. The sample was prepared using a standard high temperature laboratory esterification setup. A 1-liter, 4-neck round bottom flask reactor was set up and equipped with a heating mantle, mechanical agitation, nitrogen sparge, temperature controller and a short packed column connected to a condenser. To the flask was charged the following reactants and catalysts: 350 grams of caprylic/capric acid blend (60/40 by weight); 250 grams of POE (12) dipentaerythritol; and 0.60 grams of p-toluene sulfonic acid to act as a catalyst.

The reaction mixture was heated to 180° C. under slow nitrogen sparge and then over a period of three hours, the temperature was increased to 220° C. During that time, the acid value of the reaction mixture went to 22 mg of KOH per gram of material. The reaction mixture was cooled to 100° C. and the catalyst was neutralized with 0.30 grams of 50% sodium hydroxide. The packed column was removed and a short path condenser/receiver was attached to the flask. Vacuum (˜0.5 mm) was applied to the flask and the reaction mixture was heated to 230° C. and held at that temperature for 1 hour. The excess caprylic/capric acid was distilled over and recovered. The reaction mixture was cooled, the vacuum was released under nitrogen, and the product cooled to 80° C. and filtered through a bed of diatomaceous earth. The yield was 500 grams of the desired ester (96.0% of theory). The product had the following properties:

-   -   Acid value=0.6     -   Saponification value=200     -   Hydroxyl value=3.5     -   Viscosity @ 25° C.=95 cS (measured by CANNON FENSKE viscometer)     -   Viscosity @ 40° C.=57 cS (measured by CANNON FENSKE viscometer)

EXAMPLE 3 Comparative Analysis

The ester products of Example 1 and Example 2 were compared against pentaerythritol tetra C8/C10 prepared from high purity pentaerythritol and caprylic/capric fatty acid (60/40 blend) (“PE Tetra C8/C10”), which is a lubricant ester having the following properties:

-   -   Acid value=0.2     -   Saponification value=324     -   Hydroxyl value=4.5     -   Viscosity @ 25° C.=58 cS (measured by CANNON FENSKE viscometer)     -   Viscosity @ 40° C.=30 cS (measured by CANNON FENSKE viscometer)         Results of the comparison are illustrated in Table 3.

TABLE 3 Comparative Analysis Viscosity Projected Viscos- Pour Mol. Weight at Viscosity* ity Point Ester (g/mol) 25° C. (cS) (cS @ 25° C.) Index (° C.) PE Tetra 680 58 52 143 −8 C8/C10 Example 1 1356 99 177 230 −52 Example 2 1650 95 231 255 −50 *Projected Viscosity values are based on Series A of FIG. 1.

As illustrated by the data in Table 3, the esters of Example 1 and Example 2 have unexpectedly low viscosities, unexpectedly high viscosity index values and unexpectedly low pour points. In particular, the viscosity of each of the esters in Example 1 and Example 2 is unexpectedly lower than that of the projected value of each, based on the data of Series A in FIG. 1.

Various embodiments of the invention have been described in fulfillment of the various objectives of the invention. It should be recognized that these embodiments are merely illustrative of the principles of the present invention. Numerous modifications and adaptations thereof will be readily apparent to those skilled in the art without departing from the spirit and scope of the invention. 

That which is claimed is: 1-13. (canceled)
 14. A composition comprising at least one ester having the structure of Formula (I):

wherein R₁ is —CH₂CH₂—,

where x is 1-10; R₂, R₃, R₄, and R₅ are independently —H or —C(O)R₁₀, where R₁₀ is an alkyl, alkenyl, or aryl group having 2 to 26 carbon atoms, provided at least 3 of R₂, R₃, R₄ and R₅ are —C(O)R₁₀; and y is 1-50 or 1-20 or 1-10.
 15. A composition comprising at least one ester having the structure of Formula (II):

wherein R₁ is —CH₂CH₂—,

where x is 1-10; R₂, R₃, R₄, R₅, R₆, and R₇ are independently —H or —C(O)R₁₀, where R₁₀ is an alkyl, alkenyl, or aryl group having 2 to 26 carbon atoms, provided at least 4 of R₂, R₃, R₄, R₅, R₆, and R₇ are —C(O)R₁₀; and y is 1-50 or 1-20 or 1-10.
 16. A composition comprising at least one ester having the structure of Formula (III):

wherein R₁ is —CH₂CH₂—,

where x is 1-10; R₂, R₃, R₄, R₅, R₆, R₇, R₈, and R₉ are independently —H or —C(O)R₁₀, where R₁₀ is an alkyl, alkenyl, or aryl group having 2 to 26 carbon atoms, provided at least 70% of R₂, R₃, R₄, R₅, R₆, R₇, R₈, and R₉ are —C(O)R₁₀; y is 1-50 or 1-20 or 1-10; and z is 1-10.
 17. A lubricant comprising the composition of claim
 14. 18. The lubricant of claim 17, wherein the lubricant is silicone-free or substantially silicone-free.
 19. The lubricant of claim 17, wherein the lubricant has a viscosity index above
 110. 20. The lubricant of claim 19, wherein the lubricant has a viscosity index between about 200 and about
 250. 21. The lubricant of claim 17, wherein the lubricant has a pour point below about −10° C.
 22. The lubricant of claim 21, wherein the lubricant has a pour point between about −30° C. and about −50° C.
 23. The lubricant of claim 17, wherein the lubricant has a molecular weight and viscosity at 25° C. within a graphical region defined by a ±10% vertical offset of the line defined by the equation y=0.0649x+12.197, wherein y is the viscosity at 25° C. in cS and x is the molecular weight, the molecular weight being greater than about
 800. 24. The lubricant of claim 17, wherein the lubricant has a molecular weight and viscosity at 25° C. within a graphical region defined by a ±10% vertical offset of the line defined by the equation y=0.1008x−74.655, wherein y is the viscosity at 25° C. in cS and x is the molecular weight, the molecular weight being greater than about
 800. 25. The lubricant of claim 17, wherein the lubricant has a viscosity at 25° C. and a molecular weight within a graphical region bounded by the lines defined by the equations y=0.12x and y=0.023x+40, wherein y is the viscosity at 25° C. in cS and x is the molecular weight, the molecular weight being between about 800 and about
 6000. 26-43. (canceled)
 44. A lubricant comprising the composition of claim
 15. 45. The lubricant of claim 44, wherein the lubricant is silicone-free or substantially silicone-free.
 46. The lubricant of claim 44, wherein the lubricant has a viscosity index between about 200 and about
 250. 47. The lubricant of claim 44, wherein the lubricant has a pour point between about −30° C. and about −50° C.
 48. The lubricant of claim 44, wherein the lubricant has a molecular weight and viscosity at 25° C. within a graphical region defined by a ±10% vertical offset of the line defined by the equation y=0.0649x+12.197, wherein y is the viscosity at 25° C. in cS and x is the molecular weight, the molecular weight being greater than about
 800. 49. The lubricant of claim 44, wherein the lubricant has a molecular weight and viscosity at 25° C. within a graphical region defined by a ±10% vertical offset of the line defined by the equation y=0.1008x−74,655, wherein y is the viscosity at 25° C. in cS and x is the molecular weight, the molecular weight being greater than about
 800. 50. The lubricant of claim 44, wherein the lubricant has a viscosity at 25° C. and a molecular weight within a graphical region bounded by the lines defined by the equations y=0.12x and y=0.023x+40, wherein y is the viscosity at 25° C. in cS and x is the molecular weight, the molecular weight being between about 800 and about
 6000. 